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Coal metamorphism in the upper portion of the Pennsylvanian Sturgis Formation in Western Kentucky

Journal Article · · Geol. Soc. Am., Bull.; (United States)
Coals from the Pennsylvanian upper Sturgis Formation (Mississippian and Virginian) were sampled from a borehole in Union County, western Kentucky. The coals exhibited two discrete levels of metamorphism. The lower rank coals of high-volatile C bituminous rank were assumed to represent the normal level of metamorphism. A second set of coals of high-volatile A bituminous rank was found to be associated with sphalerite, chlorite, and twinned calcite. The latter mineral assemblages indicate that hydrothermal metamorphism was responsible for the anomalous high rank. Consideration of the sphalerite fluid-inclusion temperatures from nearby ores and coals and the time - temperature aspects of the coal metamorphism suggests that the hydrothermal metamorphic event was in the 150 to 200 C range for a brief time (10/sup 5/-10/sup 5/and yr), as opposed to the longer term (25-50m yr) 60 to 75 C ambient metamorphism.
OSTI ID:
6659202
Journal Information:
Geol. Soc. Am., Bull.; (United States), Journal Name: Geol. Soc. Am., Bull.; (United States) Vol. 94:12; ISSN BUGMA
Country of Publication:
United States
Language:
English